Unintentional boron incorporation in AlGaN layers grown by plasma-assisted MBE using highly efficient nitrogen RF plasma-sources

Device characteristics of enhancement mode double heterostructure DH‐HEMT with boron‐doped GaN gate cap layer for full‐bridge inverter circuit

“…Figure shows the comparison and variation of I ds,sat and g m values for B‐doped and Mg‐doped GaN cap DH‐HEMT extracted from I ds ‐V gs transfer characteristics of the devices for various Al content “x” in Al x Ga 1‐x N back‐barrier/buffer. The B‐doped GaN cap device exhibited highest current density (from I ds,sat = 0.6 A/mm with x = 0% to 0.27 A/mm with x = 7%) in the illustrated Al content range “x” in Al x Ga 1‐x N buffer; by contrast, the Mg‐doped GaN cap device exhibited a drop in current density (from I ds,sat = 0.3 A/mm with x = 0% to 0.12 A/mm with x = 7%) at a drain bias of 15 V. Because of the high resistive and low carrier trapping effect, the B‐doped GaN cap device achieved relatively both high ON‐state I ds,sat and peak g m and exhibited a much lower OFF‐state leakage current, indicating that this architecture provided the device with effective channel modulation than that of the Mg‐doped GaN cap device.…”

“…The interaction between B‐doping in GaN gives rise to a strong passivation effect to reduce the probability of carrier‐trapping and achieve a low device leakage current . However, at the same time, good transport properties are maintained in the conduction band leading to better conductivity and enhanced mobility of the electrons in the transport channel of 2DEG that has positive impact mainly on the current density. Compared with Mg‐doped GaN, B‐doped GaN, clearly, shows improvement in I ds and g m with reduced leakage current as shown in Figure .…”

“…Recently, only a limited number of B-doped GaN, especially on metal-organic chemical vapor deposition (MOCVD) technique, has been reported. [16][17][18] The B dopant induces dislocation inclination to reduce dislocation density in the GaN film. 19 Because the atomic radius of B is smaller than both Al and Ga and larger than N, B doping in a GaN layer induces a local strain field.…”

“…In this effort, B is found to be a highly favorable dopant with possible high doping concentration in GaN. Recently, only a limited number of B‐doped GaN, especially on metal‐organic chemical vapor deposition (MOCVD) technique, has been reported . The B dopant induces dislocation inclination to reduce dislocation density in the GaN film .…”

Stress control in thick AlN/c-Al2O3 templates grown by plasma-assisted molecular beam epitaxy

“…The possible contribution of unintentional impurities to the tensile stress in the AlN films grown under nitrogen rich conditions should be discussed, since the incorporation of any impurities increases under these conditions. One of the most probable impurities is boron atoms sputtered from the pBN RF-discharge chamber in a N 2 -plasma source, as demonstrated by Novikov et al [42] for the PA MBE of AlGaN layers using various plasma sources including the same HD-25 (Oxford Appl. Res.)…”